1. Field of the Invention
The present invention relates to an electromagnetic valve actuator to control the intake and exhaust valves of a four-cycle internal combustion engine. More particularly, it relates to such a device having computer-controlled electromagnetic contacts to automatically and continuously adjust the timing and duration of the valves.
2. The Prior Art
Most four-cycle internal combustion engines utilize a cam shaft or an overhead cam shaft to control the valves. A standard cam shaft includes a power-draining drive gear, valve lifters and heavy return springs, all of which drain power from the engine. An overhead cam shaft, although avoiding the valve lifters, still adds an additional load to the engine.
In addition, these cam shafts are not adjustable. A cam shaft with short duration cam lobe profiles benefit low rpm torque, fuel economy and emissions. A long-duration profile, on the other hand, produces greater horsepower, with correspondingly decreased low rpm power and economy. Engine designers must balance these two extremes for sufficient performance and acceptable emissions under all conditions. Since cam shafts by their construction cannot adjust, the engines cannot produce their optimum power at all times.
Attempts have been made to create electromagnetic valve control systems. For example, U.S. Pat. Nos. 4,942,851, 4,515,343, 4,794,890, 4,312,494, 3,853,102, 4,544,986 and 4,841,923 all disclose electromagnetic valve control systems. However, all of these systems operate directly on the valve stem itself. With such arrangement, the distance between the electromagnets is equal to the valve lift. The greater the distance between electromagnets, the more power needed to move the valve stem and hence, the valve, into either of its two terminal positions.
Furthermore, these systems are not continuously adjustable. In other words, these electromagnetic systems cause the valve to open and close at a predetermined point in the engine's revolutions. The prior art systems do not allow the valve timing to be adjusted continuously as the rpm and load change. The configuration of the prior art devices do not allow for adjustment of the valve lift.